Floating barrier

ABSTRACT

The invention concerns one or more floating barriers for use together with a conventional floating barrier for use in collecting oil on a water surface. The floating barriers are of the kind where the submerged part is partially penetrable for water and oil, thereby providing an impeding but not blocking effect on a passing flow of water. The function of the floating barriers is based on the fact that by disposition upstream relative to the conventional floating barrier and together with the latter they will constitute a total system which can be moved through an oil-contaminated body of water with substantially greater speed than a conventional floating barrier, without leaking oil behind the floating barrier system. The invention particularly concerns conditions of the geometry, spacing and draught of the water-penetrable liquid barriers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns a floating barrier system including aconventional floating barrier and at least two liquid-penetrableauxiliary barriers, where the at least two liquid-penetrable auxiliarybarriers are arranged in front of a conventional floating barrier, andwhere the liquid-penetrating effect is achieved by a given degree ofperforation, wherein the conventional liquid barrier as well as the atleast two liquid-penetrable floating barriers extend over a horizontallength from a first end to a second end at a vertical depth from anupper edge to an lower edge.

2. Description of Related Art

By prior art conventional floating barriers, the submerged part istypically constituted by an approximately vertical impenetrable wallwhich will block a given liquid flow that may try to pass it. As theliquid flow is also prevented from passing over the submerged part dueto the overwater part, which is typically constituted by buoyant bodies,the liquid flow is forced to pass under the submerged part. This entailsa local increase in speed of the water flow which is to pass under thesubmerged part. This means that a conventional floating barrier which ismoved through a liquid flow at e.g. 0.5 m/s locally can have liquidflows around the submerged part, particularly in a zone in front of thefloating barrier (head wave effect), with double or triple speed. Thisoccurs in particular in a zone upstream in relation to the floatingbarrier and in a area where a possible oil contamination can be located.By exceeding about 1 m/s in difference of the speed in the boundarylayer between the oil layer and the water flow, entrainment of oil dropswill begin, the drops being moved under the submerged part of theconventional floating barrier which hereby is provided a leakage. Byincreased difference in speed, this effect will be increased and largeamounts of oil will be entrained down under the floating barrier. Formany years, this phenomenon has been known as the limiting element inthe use of floating barriers which has caused the used towing vessels tobe limited in manoeuvring and the oil collecting operation to be verytime-consuming as well.

Use of supplementary, partially penetrable floating barriers in order tocounteract the above limitations to the efficiency of floating barriershas been described and tested in the period 1990-1999 by variousresearch groups. By these tests it has appeared that it is possible toincrease the operational speed by a factor 2-3, but by using the presentinvention this factor is increased to more than 4.

U.S. Pat. No. 3,771,662 discloses a solution where a plurality ofsuccessive floating barriers are applied where the rearmost floatingbarrier is a traditional floating barrier and where at the upper edge oftwo floating barriers in front are arranged a series of uniformapertures. Water and oil flow from the surface through these uniformopenings when the floating barrier is towed through the water. These arevery solid floating barriers which only can be moved at a low speed inorder not to form a so-called head wave effect where water and oil areforced to speed up so to say and to be entrained in a flow under thefloating barriers.

In order to avoid the inexpedient effect of head wave and oil escapingthe floating barrier, a bottom is arranged in U.S. Pat. No. 3,771,662between two floating barriers such that in principle a basin is formedbetween the latter. This bottom is arranged at an angle with horizontalsuch that the depth increases towards the rearmost of the two floatingbarriers in question. All water is thus to flow through a relativelysmall number of apertures in the floating barrier at its upper edge andout of the mentioned basin through a number of apertures at the bottomof it and close to the rearmost of the floating barriers in question.Thus it is the area of the mentioned apertures that determine how fastthe floating barrier can be moved and still be usable for efficientcollection.

U.S. Pat. No. 3,771,662 indicates a solution with large resistance whendrawn through the water and which only will have a collecting effect ata very low speed, which obviously means that this is a less efficientsolution which does not live up to the present demands to a rapid andefficient solution which in that case can prevent a natural catastropheby rapid collection of spilled oil.

SUMMARY OF THE INVENTION

It is the purpose of the invention to indicate a floating barrier systemwhere the above mentioned drawbacks are counteracted and where it ispossible to perform collection of e.g. oil from a water surface at aspeed which is preferably about 300 to 400% greater than hitherto.

As mentioned in the introduction, the invention concerns one or morefloating barriers for use together with a conventional floating barrierfor use in collecting oil on a water surface. The floating barriers areof the kind where the submerged part is partially penetrable for waterand oil, thereby providing an impeding but not blocking effect on apassing flow of water. The function of the floating barriers is based onthe fact that by disposition upstream relative to the conventionalfloating barrier and together with the latter they will constitute atotal system which can be moved through an oil-contaminated body ofwater with substantially greater speed than a conventional floatingbarrier, without leaking oil behind the floating barrier system. Theinvention particularly concerns conditions of the geometry, spacing anddraught of the water-penetrable liquid barriers. The new feature of afloating barrier system according to the invention as indicated in claim1 is that at least one of the at least two liquid-penetrable auxiliarybarriers is made with a degree of perforation which is different from atleast one other liquid-penetrable auxiliary barrier. Hereby is achieveda graduated retardation of the water whereby an appreciably increasedspeed can be applied during towing of the floating barrier system bycollection of spilled oil.

In a preferred variant of a floating barrier system according to theinvention, the floating barrier system is arranged with a front/firstliquid-penetrable auxiliary barrier with a first degree of perforation,and at least with one other liquid-penetrable auxiliary barrier with asecond degree of perforation, wherein the front liquid-penetrableauxiliary barrier is provided with a greater degree of perforation thana subsequent liquid-penetrable auxiliary barrier. Hereby is introduced agraduated degree of penetrability between two or more floating barriers(auxiliary barriers) disposed upstream. However, this is so that thefloating barrier encountering the liquid flow first has the greatestpenetrability and thereby the lowest blocking action, the next slightlylower penetrability and possibly a third with even lower penetrability.This means that a passing liquid flow is gradually decelerated, thusencountering the conventional blocking floating barrier at a speed whichdoes not give any problems with regard to entrainment of oil and therebyleakage in the system. At the same time, the graduated retardationeffect means that none of the penetrable auxiliary barriers willencounter the liquid flow at a critical speed relative to the “headwave” effect.

In an embodiment of the invention, a floating barrier system will beadapted such that that the degree of perforation of a liquid-penetrableauxiliary barrier is substantially uniform in its full horizontallength.

In another embodiment of the invention, a floating barrier system may beadapted such that that the degree of perforation of a liquid-penetrableauxiliary barrier varies over its horizontal length. By this variant ofthe invention is avoided that the effect of an unavoidable anglingrelative to the direction of flow is avoided. It is thus possible toadapt the size of the perforations of the auxiliary barrier such thatthe projected area facing in the direction of movement is more or lessuniform irrespective of the auxiliary barrier having a U-shape, as itappears from the subsequent Figures.

In another embodiment of this embodiment, graduation of the draught ofupstream disposed penetrable floating barriers forms a part. A floatingbarrier system according to the invention can be arranged such that theindividual liquid-penetrable floating barriers have different verticaldepth and where the front/first liquid-penetrable floating barrier isprovided with the greatest depth. However, it may also be so that thefront/first liquid-penetrable floating barrier has the lesser depth andthat a subsequent liquid-penetrable floating barrier is provided withthe greater depth. This will also entail a desirable graduateddeceleration of the liquid flow.

In yet a preferred embodiment of this invention, at least oneliquid-penetrable floating barrier may include one or more verticalcrossbars extending from the upper edge of the at least oneliquid-penetrable floating barrier towards its lower edge. The verticalcrossbar or crossbars is/are disposed with suitable spacing with theobject of ensuring vertical straightness of the auxiliary barriers inthe liquid flow. This means that the penetrability of the auxiliarybarriers is kept constant in vertical direction without needinggraduation of the perforation.

Finally, the invention includes a characterisation of the mutual spacingof the constituent penetrable floating barriers and the distance to theblocking conventional floating barrier behind. A preferred embodiment ofa floating barrier system according to the invention can be adapted suchthat the spacing between the individual auxiliary barriers is made suchthat the spacing (b) is between 80 and 150% of the spacing (c), and thatthe spacing (a) is between 80 and 150% of the spacing (b).

The invention is explained in more detail in the following withreference to the drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a complete floating barrier system with three partiallypenetrable auxiliary barriers disposed upstream.

FIG. 2 shows a segment of the floating barrier system showing that theindividual auxiliary barriers can have varying degree of perforation.

FIG. 3 shows a segment of the floating barrier system showing that theindividual auxiliary barriers have horizontally varying degrees ofperforation.

FIG. 4 shows a segment of the floating barrier system showing that theindividual auxiliary barriers have varying draught.

FIG. 5 shows a segment of the floating barrier system showing that theindividual auxiliary barriers have built-in vertical crossbars.

FIG. 6 shows a segment of the floating barrier system showing that theindividual auxiliary barriers are provided with varying spacing.

DETAILED DESCRIPTION OF THE INVENTION

In the explanation of the Figures, identical or corresponding elementswill be provided with the same designations in different Figures.Therefore, no explanation of all details will be given in connectionwith each single Figure/embodiment.

In FIGS. 1-5 is seen the conventional floating barrier 1 which in thissystem is arranged in U-shape. To this is fastened auxiliary barriers 2,3, and 4 in upstream direction. The conventional floating barrier isprovided with consecutive buoyant bodies 5 which may be air-filled orwith a permanent buoyancy means, e.g. plastic foam. These have thepurpose of ensuring a stable position for the floating barrier at sea,also by possible wave action. The submerged part 6 is constituted by animpenetrable wall of e.g. reinforced rubber or plastic film. Typically,the wall has a draught corresponding to 0.5 to 1.5 times the diameter ofthe buoyant bodies (the freeboard). Along the lower edge of the wall isfastened a ballast 7 which can be in the form of an iron chain, leadrope or bolted metal blocks. The purpose of the ballast is to contributeto the stable position of the floating barrier at sea and to ensurevertical position of the submerged part. The auxiliary barriers 2, 3 and4 on FIGS. 1-5 are also provided with buoyancy means 8 and ballast 9which have the same functions as in the conventional floating barrier.

In FIG. 2 is shown that the auxiliary barriers 2, 3 and 4 have differentdegree of perforation 10, 11 and 12 providing varying penetrability fora liquid flow. The degree of perforation of the auxiliary barriers willtypically be between 60 and 90%. This means that the open areaconstitutes between 60 and 90% of the total area of the submerged part.In the embodiment shown here, auxiliary barrier 2 which is disposedfarthest upstream has a preferred degree of perforation of 75-85%,auxiliary barrier 3 a degree of perforation of 70-80% and auxiliarybarrier 4 a degree of perforation of 65-75%.

In FIG. 3 is shown that the auxiliary barriers 2, 3 and 4 havehorizontally varied degree of perforation 13 and 14, respectively. Thepreferred embodiment of the latter entails that the flanks of theauxiliary barrier will have an angling relative to the liquid flowencountering the centre line of the floating barrier system will have adegree of perforation which compensates for this fact. This means thatthe projected degree of perforation becomes the same as in the centralpart of the auxiliary barrier. The performed perforation can either bemade as stepwise variations or as a successive variation.

In FIG. 4 is shown that the auxiliary barriers have varied draughts 15,16, and 17, respectively. In the embodiment preferred here, auxiliarybarrier 15 is reduced to between 60 ad 90% of the draught of theconventional floating barrier. Auxiliary draught 16 is reduced tobetween 70 and 100% and auxiliary barrier 17 to between 80 and 100%.

In FIG. 5 appears that the individual auxiliary barriers are providedwith vertical crossbars 18. In the embodiment shown here, these aredisposed with spacing (d) corresponding to 100-450% of the total height(e) of the auxiliary barriers.

In FIG. 6 is shown that the spacing (a) and (b) of the individualauxiliary barriers and the distance to the conventional floating barrier(c) are varied. In the preferred embodiment here, the spacings betweenthe individual auxiliary barriers 2, 3 and 4 are made such that thespacing (b) is between 80 and 150% of the spacing (c), and the spacing(a) is between 80 and 150% of the spacing (b).

1. A floating barrier system including a conventional floating barrierand at least two liquid-penetrable auxiliary barriers, where the atleast two liquid-penetrable auxiliary barriers are arranged in front ofa conventional floating barrier, and where the liquid-penetrating effectis achieved by a given degree of perforation, wherein the conventionalliquid barrier as well as the at least two liquid-penetrable floatingbarriers extend over a horizontal length from one end to another end ata vertical depth from an upper edge to an lower edge, wherein at leastone of the at least two liquid-penetrable auxiliary barriers are madewith a degree of perforation which is different from at least one otherliquid-penetrable auxiliary barrier.
 2. A floating barrier systemaccording to claim 1, wherein the liquid-penetrable system is arrangedwith a front/first liquid-penetrable auxiliary barrier with a firstdegree of perforation, and at least with one other liquid-penetrableauxiliary barrier with a second degree of perforation, wherein the frontliquid-penetrable auxiliary barrier is provided with a greater degree ofperforation than a subsequent liquid-penetrable auxiliary barrier.
 3. Afloating barrier system according to claim 1, wherein the degree ofperforation of a liquid-penetrable auxiliary barrier is substantiallyuniform in its full horizontal length.
 4. A floating barrier systemaccording to claim 1, wherein the degree of perforation of aliquid-penetrable auxiliary barrier varies over the horizontal length.5. A floating barrier system according to claim 1, wherein theindividual liquid-penetrable floating barriers have different verticaldepths.
 6. A floating barrier system according to claim 5, wherein thefront/first liquid-penetrable floating barrier is provided with agreater depth than a subsequent liquid-penetrable floating barrier.
 7. Afloating barrier system according to claim 5, wherein the front/firstliquid-penetrable floating barrier is provided with a lesser depth thana subsequent liquid-penetrable floating barrier.
 8. A floating barriersystem according to claim 1, wherein at least one liquid-penetrablefloating barrier includes one or more vertical crossbars extending fromthe upper edge of the at least one liquid-penetrable floating barriertowards its lower edge.
 9. A floating barrier system according to claim1, wherein the spacing between the individual auxiliary barriers is madesuch that the spacing (b) is between 80 and 150% of the spacing (c), andthat the spacing (a) is between 80 and 150% of the spacing (b).